The meaning of "Sinister" in various phrases and sentences

This is from a twitter poll. The RT means that the reader should retweet the original tweet once he or she has voted. The first sentence is asking if people think that the incidents that occurred at Celtic are connected in a sinister manner and not simply isolated events.

At the end of this first stanza, the writer fragments the last sentence to draw attention to two important facts of his poem. The expression "ice - block - cold eyes" probably means their eyes are sad, unfriendly and unhappy and these people are no longer able to reveal anything about their personal thoughts and feelings. They are like robots, incapable of expressing and feeling anything. The second part of this fragmented sentence reinforces the sentiment of hostility and bitterness (that) the writer feels towards those who changed their attitudes and behaviours for the worse. The sentence "they search behind his shadow" can mean that whenever he leaves a place they look back at him and analyse him behind his back. The writer paints a predatory and sinister image of these people, as they were his enemies and wanted to hurt him.